This invention related to a process for coating surfaces of various materials with a radiation curable coating. More specifically, this invention relates to a process for applying a radiation curable coating to a panel surface wherein the coating is cured to a predetermined surface gloss.
In the furniture and wood finishing industry, it is highly desirable for natural and simulated wood surfaces to have the appearance of a natural hand-rubbed finish. Such a hand-rubbed finish is normally achieved with a plurality of sprayed lacquer coatings, and the last coating is hand-rubbed to the desired surface gloss. This surface gloss is quantitatively measurable with equipment such as a 60.degree. glossometer, with a surface finish of approximately 60 gloss being presently popular with furniture. However, hand-rubbed lacquer finishes have not been totally satisfactory in that the hand-rubbing is a relatively costly step which substantially increases the cost of the furniture. Further, while lacquer coatings are relatively easy to hand rub, they are also highly susceptible to damage from scratches, cigarette burns, water marks, etc. Accordingly, it is desirable to simulate esthetically popular lacquer finishes on natural and simulated wood surfaces with a more durable finish which does not require any expensive hand rubbing.
In the prior art, laminated plastic materials such as those sold under the trademark Formica have been widely used to simulate natural wood surfaces. Such laminated plastics typically have a wood grain design printed thereon, and are retained on furniture or other substrates by an adhesive. Laminated plastics are advantageous in that they exhibit relatively good scratch, water, and heat resistance properties. However, the use of plastic laminated surfaces is readily apparent from an inspection of the furniture, and thereby undesirably limits the value of the furniture.
A more suitable approach in the prior art for simulating hand-rubbed wood finishes has been to coat the surface of a furniture panel with a radiation-sensitive coating such as an ultraviolet curable, polyester resin. See, for example, U.S. Pat. Nos. 3,511,687 and 3,669,716. After coating, the panel is subjected to a source of radiation such as ultraviolet producing mercury vapor lamps to cure the coating without hand rubbing to a hard, durable and scratch-resistant finish. However, the cured panel surface typically has an appearance which does not show the minute scratches obtained using a hand-rubbed finishing step. Further, radiation sensitive coatings of the prior art have not been usable for achieving a surface phenomena known as "flop", wherein the surface gloss of a furniture panel varies according to the angle of viewing. This phenomena does occur by hand-rubbing the furniture panel, and is therefore a highly desirable surface characteristic. However, because of their high durability and scratch resistance, radiation curable coatings cannot be hand-rubbed satisfactorily.
It is therefore an object of this invention to provide a process for imparting an accurately simulated hand-rubbed surface finish to a natural or simulated wood panel. Further, it is an object of this invention to provide a process for selectively obtaining different final surface glosses using a radiation sensitive surface coating having optimum scratch, water, and heat resistance properties.